This invention is directed generally to rendering venous valve leaflets incompetent for in-situ arterial bypass in patients requiring arterial reconstruction for chronic limb-threatening ischemia. More particularly, this invention is directed to a venous valve cutter having unique improved cutting surfaces to facilitate the incision of the leaflets and a unique irrigation system to minimize frictional forces on the endothelium of the vein when introducing and withdrawing the cutter.
A common form of chronic limb-threatening ischemia, femorotibial, obstructive disease, typically is treated by using the greater saphenous vein as a bypass conduit. Traditionally, this vein has been removed from its anatomic bed and reversed to overcome the obstruction to flow from its one-way valves. The distal end of the "reversed flow" greater saphenous vein is then grafted to the femoral artery and its proximal end is grafted to the outflow artery beyond the obstruction.
There are a number of problems inherent in the use of a reversed flow saphenous vein as a bypass conduit. The narrow distal end of the vein may not permit enough arterial in-flow from its new parent vessel, whereas the wide proximal end of the vein makes an anastomosis to the 2-3 millimeter distal outflow vessel cumbersome. Also, the body of the vein may twist or compress and be damaged during the vein removal, reversal and replacement process and it is difficult to preserve the very sensitive endothelial layer of the vein during the removal and replacement process. Furthermore, the process may impair the blood vessel's blood supply (the vasa vasorum).
Bypass procedures in which a vein is used as it lies anatomically within the body, without removal, reversal and replacement, i.e., "in-situ situ vein bypasses", generally overcome most problems associated with removing, reversing and replacing the vein. This is most commonly accomplished in treating femorotibial disease by moving a valve cutter through the saphenous vein to incise the venous valve leaflets.
Since Carrel and Guthrie's publication of the techniques required for a small vessel anastomosis, vascular surgeons have attempted infrainguinal distal revascularizations. The advantage of the in-situ technique for saphenous vein bypass are first that the narrow end is anastomosed to the smaller artery distally with the graft tapering in the appropriate direction. This improves the hemodynamics at both anastomoses. A second consideration is that the adventitial blood supply to the vein is preserved to help protect the endothelial lining of the vein.
Typically, in performing this procedure either the distal end of the vein is anastomosed to the femoral artery to allow arterial blood to pass into the vein or a saline solution is pumped through a cannula into the vein to provide the required pressure to distend the vessel and close the valves. These procedures are performed to ensure that the valve cutter will meet and incise the valve leaflets in their closed, extended position. Once all of the valves are made incompetent, the vein becomes suitable for use as an arterial bypass conduit.
Unfortunately, it is quite difficult using currently available valve cutters, to efficiently and consistently incise and render the valves incompetent without damaging the endothelium of the vein or even piercing the vein wall. The various currently available valve cutter devices are difficult to manipulate, often do not center and catch the valve leaves properly, and can cause significant damage to the vein due to intimal contact between the surfaces of the cutting head and the vein wall and tearing at the points of valve attachment to the vessel wall.
U.S. Pat. No. 3,837,345, entitled "Venous Valve Snipper", describes a device for incising valves in vein grafts to bypass blocked arteries. This device is not intended to be used in-situ. The instrument has a closed position and an open position: it is maneuvered past the venous valves in the direction of blood flow, opened and withdrawn whereby sharp spikes spear and impale the venous valve leaflets which are then hopefully incised by closing the device in a scissors-like motion.
U.S. Pat. No. 4,493,321, entitled "Venous Valve Cutter for the Incision of Valve Leaflets In-situ", describes a valve cutter in the shape of a reverse arrowhead for preparing a vein in-situ for an arterial bypass. The valve cutter includes a rounded leader, a cutting blade enclosed in a protective support, a torsionally rigid rod connecting the leader to the cutting blade, and a catheter attached to the cutting blade support with suture material. The valve cutter is used by making proximal and distal incisions in the vein, passing a rod through the vein, attaching the valve cutter and pulling it down the vein while introducing fluid through the attached catheter to close the valves before incising them, and then returning the valve cutter assembly to the proximal incision. The orientation of this device must be continuously controlled to prevent the cutting blade from catching and tearing the orifice wall of a contributing venous branch and to ensure engagement and incision of both leaflets of each valve.
U.S. Pat. No. 5,047,041, entitled "Surgical Apparatus for the Excision of Vein Valves In-situ", describes a valve cutter in which a circular cutting head affixed to a cable is preceded by a dilating segment also affixed to the cable. The circular cutting edge has series of rounded guide teeth which are intended to guide the valve leaflets into cutting grooves which are supposed to engage and then cut the valve leaflets. Unfortunately, the rounded unsharpened guide teeth pull, stretch and likely irregularly tear the valve leaflets before any cutting can begin.